Hose clamps of the type under discussion (see for example U.S. Pat. No. 4,583,268) are particularly intended and suitable for use in hose systems with medium internal pressures, for example for cooling systems of automotive vehicles where internal pressures of no more than 2 bar are expected under operating conditions. Customarily such hose systems are tested for up to 3 bar. The pressure-proof seating of a hose end on a connecting piece of such a hose system is assured by the elasticity of the hose end itself, which mostly is a rubber hose, a rubber/plastic hose with a fabric cover, etc., and also by the spring force of the hose clamp discussed above.
Thus the known hose clamp is not clamped by means of a separate clamping element, for example a clamping screw, in order to obtain the pressure-proof seating of a hose end on a connecting piece; instead the spring force of the correspondingly highly prestressed hose clamp assures pressure-proof seating. The force which needs to be exerted on the clamping ends of the hose clamp by a tool must be correspondingly great in order to spread the hose clamp against its inherent spring force to a considerably larger and mostly maximally limited diameter. This diameter must be sufficient to move the hose clamp easily across the hose end seated on the connection piece all the way to its intended position.
When installing a hose with the known and previously described hose clamp, the hose clamp is first gripped and spread with a spreading tool and is then pushed in its spread state onto the connection piece or on the hose end. During the entire installation which then follows the hose clamp must be kept spread open by means of the spreading tool. When the hose end has been pushed onto the connection piece and has been further pushed over a form-fitting circular bead possibly provided there, the spread-open hose clamp is moved to the intended position by means of the spreading tool, the spreading tool is detached and the hose clamp released. The hose clamp springs back in the direction of its released and clamping state, becomes attached to the hose end and clamps the latter onto the connection piece.
The above description of the installation with a known hose clamp makes it clear that one hand is required for manipulating the hose clamp with the spreading tool and another hand for the manipulation of the hose end itself. This plus the fact that the hose clamp can only be manipulated with a spreading tool and by bringing considerable spreading force to bear, causes problems in installation and other operational use.